Carboxylic acid production process employing solvent from esterification of lignocellulosic material

ABSTRACT

Methods and apparatus for producing a carboxylic acid employing a solvent from esterification of lignocellulosic materials. An acid-containing composition from esterification of lignocellulosic materials can be employed in the oxidation of para-xylene to terephthalic acid. The acid-containing composition can comprise acetic acid, acetic anhydride, and one or more terpenes.

RELATED APPLICATIONS

This application claims the priority benefit of U.S. Provisional Pat.App. Ser. No. 61/021,153 titled “CARBOXYLIC ACID PRODUCTION PROCESSEMPLOYING SOLVENT FROM ESTERIFICATION OF LIGNOCELLULOSIC MATERIAL,”filed Jan. 15, 2008, the entire disclosure of which is incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to carboxylic acid productionprocesses. More specifically, the present invention concerns equipmentand processes for producing carboxylic acids employing solventoriginating from a process involving esterification of lignocellulosicmaterial.

2. Description of the Prior Art

In conventional terephthalic acid (“TPA”) production processes,para-xylene undergoes oxidation to form crude terephthalic acid (“CTA”)particles. A slurry of CTA particles can then undergo purification toform purified terephthalic acid (“PTA”) particles. A purified slurrycomprising PTA particles and a liquid phase can then be treated in aproduct isolation zone to isolate at least a portion of the PTAparticles. During the TPA production process, a solvent is typicallyintroduced into the oxidizer along with the para-xylene. Additionally,solvent can be added during the purification step to replenish solventlost during the oxidation process due to decarboxylation. This solventinitially acts as a carrier fluid for the para-xylene, and later as acarrier fluid for the TPA formed in the oxidation reactor. Though theseprocesses are generally known in the art, given its high global demandimproved production processes for TPA are continually needed.

In another process, lignocellulosic material (e.g., wood) can undergoesterification (e.g., acetylation) for purposes of, inter alia, makingthe lignocellulosic material more dimensionally stable, more weatherresistant, and/or insect resistant. In a typical lignocellulosicmaterial esterification process, the lignocellulosic material iscontacted with a compound containing an acetyl group, such as aceticanhydride. The hydroxyl groups in the lignocellulosic material can thenreact with acetyl groups from the anhydride, thus forming acetylatedlignocellulosic material and an acid-containing composition. When aceticanhydride is employed in this process, acetic acid is produced as abyproduct. A portion of the acetic acid can be recycled in order to formmore anhydride by, for example, a cracking process and reaction withketene. However, at least a portion of the acid can be removed from theprocess in order to control the level of impurities, such as, forexample, terpenes.

SUMMARY OF THE INVENTION

In one embodiment of the present invention, there is provided a processfor producing a carboxylic acid. The process of this embodimentcomprises oxidizing an oxidation feed comprising at least one oxidizablecompound and at least one solvent comprising a monocarboxylic acid,where at least a portion of the monocarboxylic acid originated from awood acetylation process.

In another embodiment of the present invention, there is provided aprocess for producing a carboxylic acid. The process of this embodimentcomprises (a) contacting at least one lignocellulosic material with acompound containing at least one acetyl group to thereby produce anacetylated lignocellulosic material and an acid-containing composition;and (b) introducing at least a portion of the acid-containingcomposition and an oxidizable compound into a carboxylic acid productionprocess, where the acid-containing composition comprises acetic acid.

In yet another embodiment of the present invention, there is provided aprocess for producing a carboxylic acid. The process of this embodimentcomprises oxidizing an oxidizable compound in an oxidation reactor inthe presence of at least one solvent. The solvent comprises aceticanhydride in an amount of at least 0.01 weight percent based on thetotal weight of the solvent.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

A preferred embodiment of the present invention is described in detailbelow with reference to the attached drawing figures, wherein:

FIG. 1 is a process flow diagram of a wood acetylation process,particularly illustrating a configuration where acetic acid is crackedto form acetic anhydride and water, and acetic anhydride is routed to anacetylation reactor for acetylating wood; and

FIG. 2 is a process flow diagram illustrating a system for theproduction and purification of carboxylic acid constructed in accordancewith the present invention, particularly illustrating a configurationwhere the crude slurry from the oxidation reactor is subjected topurification, the resulting purified slurry is subjected to productisolation, and a portion of the mother liquor from the product isolationzone is employed as a feed to a purge treatment system.

DETAILED DESCRIPTION

In accordance with one embodiment of the present invention, alignocellulosic material (e.g., wood) can undergo an esterification(e.g., acetylation) process to produce an esterified lignocellulosicmaterial (e.g., acetylated wood) and an acid-containing composition. Atleast a portion of this acid-containing composition can be employed in aprocess for producing carboxylic acid (e.g., terephthalic acid (“TPA”)).

The above-mentioned esterification process employed in the presentinvention can be any known esterification process for generating anesterified lignocellulosic material and an acid-containing composition.In one embodiment, the esterification process can be any known processfor producing acetylated wood. As used herein, the term “acetylated”shall denote a substance that has been chemically altered to contain oneor more acetyl groups. In general, an esterification process of thepresent invention can include contacting a lignocellulosic material withan impregnating compound capable of esterifying the lignocellulosicmaterial. As will be discussed in further detail below, theesterification can be performed under pressure and/or under conditionsof increased temperature. Furthermore, the esterification can beperformed in a suitable reaction vessel.

The lignocellulosic material in the above-mentioned esterificationprocess can be any lignocellulosic material capable of being esterified.As used herein, the term “lignocellulosic” shall denote any materialthat contains lignin along with cellulose and/or hemicellulose.

In one embodiment, the lignocellulosic material suitable for use in thepresent invention can be wood. When wood is employed as thelignocellulosic material, the form of the wood suitable for use in thepresent invention is not limited and can be employed in any dimension orshape. In one embodiment, the wood can be in the form of veneers,boards, planks, squared timber, beams or profiles, wood particles, woodflakes, or wooden end products. When wood particles are employed, thewood scrap can be in the form of wood flour, wood fibers, and woodshavings obtained from wood processing. Mixtures of wood scraps can alsobe used. Additionally, the species of wood is not critical, as anyspecies of wood can be employed in the present invention. In oneembodiment, the wood employed in the present invention can comprisebroad-leaved or coniferous wood (generally speaking, hard or soft woodsrespectively).

The lignocellulosic material suitable for use in the above-mentionedesterification process can contain water. In one embodiment, thelignocellulosic material can initially contain at least about 15 weightpercent water, at least about 17 weight percent water, or at least 19weight percent water prior to esterification. In one embodiment, thelignocellulosic material can be dewatered to produce a dewateredlignocellulosic material having a water content of less than about 15weight percent water, less than about 10 weight percent water, or lessthan 5 weight percent water. Any method known in the art can be employedto achieve the desired water content of the lignocellulosic materialprior to esterification. In one embodiment, kiln drying and/or drying byacetic acid impregnation coupled with vacuum/pressure cycles can beemployed to achieve the desired water content.

The impregnating compound of the present invention can be any compoundcapable of reacting with one or more hydroxyl groups in thelignocellulosic material to thereby form an esterified lignocellulosicmaterial and an acid-containing composition. In one embodiment, theimpregnating compound can be an anhydride. Examples of anhydridessuitable for use in the present invention include, but are not limitedto, acetic anhydride, propionic anhydride, butyric anhydride, pentanoicanhydride, hexanoic anhydride, and their isomers, as well as any mixedanhydrides containing acetic, propionic, butyric, pentanoic, and/orhexanoic moieties and their isomers. In one embodiment, the impregnatingcompound can predominately comprise acetic anhydride. As used herein,the terms “majority,” “primarily,” and “predominately” shall mean morethan 50 percent. In another embodiment, the impregnating compound cancomprise acetic anhydride in an amount of at least about 70, at leastabout 80, or at least 95 weight percent.

In one embodiment, the impregnating compound can be employed in thepresent invention as substantially the sole reagent. In anotherembodiment, the impregnating compound can be used in combination withother compounds, such as, for example, tertiary amines, acetone,pyridine, aromatic hydrocarbons, and/or chlorinated hydrocarbons.Furthermore, the impregnating compound can comprise acetic acid.Additionally, one or more catalysts can be employed in theesterification of the lignocellulosic material.

The amount of impregnating compound employed can be any amountsufficient to increase the total acetyl content of the startinglignocellulosic material by at least 1 weight percent, at least 2 weightpercent, or at least 3 weight percent, based on the total weight of thelignocellulosic material. The total acetyl content of thelignocellulosic material can be determined according to thesaponification method, as is known in the art. In one embodiment, theamount of impregnating compound absorbed by the lignocellulosic materialcan be in the range of from about 50 to about 250 weight percent, in therange of from about 65 to about 200 weight percent, or in the range offrom 80 to 150 weight percent, based on the weight of the dewateredwood.

As mentioned above, the esterification process employed in the presentinvention can be performed at elevated pressure and/or temperature. Thepressure and temperature employed in the present invention can be anypressure and temperature suitable to increase the total acetyl contentof the starting lignocellulosic material by at least 1 weight percent,at least 2 weight percent, or at least 3 weight percent, based on thetotal weight of the lignocellulosic material. In one embodiment, theesterification can be performed at temperatures of at least about 40°C., at least about 65° C., or at least 90° C. Additionally, theesterification can be performed at a pressure of at least about 20pounds per square inch gauge (psig), in the range of from about 25 toabout 150 psig, in the range of from about 35 to about 125 psig, or inthe range of from 50 to 100 psig.

The acid-containing composition originating in the esterificationprocess can vary depending on the chosen impregnating compound. Theacid-containing composition of the present invention can comprise anyacid derivative of the above-described impregnating compounds. In oneembodiment, the acid-containing composition can comprise an organic lowmolecular weight monocarboxylic acid having from 1 to 6 carbon atoms.For example, the acid-containing composition can comprise acetic acid,propionic acid, butyric acid, pentanoic acid, and/or hexanoic acid. Inone embodiment, the acid-containing composition predominately comprisesacetic acid. In another embodiment, the acid-containing composition cancomprise acetic acid in an amount of at least about 70, at least about80, or at least 95 weight percent.

Following esterification, the esterified lignocellulosic material can besubject to a drying process so as to remove any excess impregnatingcompound and residual acid remaining in the lignocellulosic material. Inone embodiment, the drying process can be performed in the same reactionvessel as the esterification step. The drying process can be any dryingprocess known in the art capable of lowering the free acid content ofthe esterified lignocellulosic material to any desired level. Examplesof drying processes that can be employed in the present inventioninclude, but are not limited to, application of heat with inert gas(e.g., nitrogen) flow, addition of steam to the reaction vessel,addition of water to the reaction vessel, or drying in a kiln which canbe equipped to collect any acid removed via condensation.

FIG. 1 illustrates an example of a lignocellulosic materialesterification process suitable for use in the present invention. Inparticular, FIG. 1 depicts a wood acetylation process where wood can beinserted into an acetylation vessel 10. Fresh acetic acid can beintroduced into holding tank 12 via line 14. In one embodiment, thefresh acetic acid can be glacial acetic acid. As used herein, the term“glacial acetic acid” denotes acetic acid having a purity of at least99.8 percent by weight. As will be discussed in more detail below, thefresh acetic acid in holding tank 12 can be combined with recycledacetic acid from acetylation vessel 10. Once combined, at least aportion of the acetic acid can be routed to cracking vessel 16 via line18.

In cracking vessel 16, at least a portion of the acetic acid can becracked to produce water and an intermediate ketene; thereafter, theacetic acid and ketene react to form acetic anhydride. In oneembodiment, at least about 50, at least about 70, or at least 90 weightpercent of the acetic acid introduced into cracking vessel 16 is crackedto eventually form water and acetic anhydride. Cracking of the aceticacid in cracking vessel 16 can be accomplished by any cracking methodsknown in the art that are capable of cracking acetic acid to eventuallyform acetic anhydride and water. For example, cracking of the aceticacid can be accomplished by thermal cracking and/or by chemicalcracking, such as, for example, catalytic cracking. In anotherembodiment, the acetic acid can be subject to any ketene process knownin the art suitable for converting acetic acid into acetic anhydride.Additionally, it should be noted that the acetic anhydride useful in thepresent invention is not limited by the method of its production, asacetic anhydride produced by any method can be used in the process ofthe present invention.

Water produced from the cracking process can be routed out of crackingvessel 16 via line 20. Acetic anhydride produced in cracking vessel 16can be routed to acetylation vessel 10 via line 22. It should be noted,however, that acetic anhydride useful in the esterification process ofthe present invention is not limited to that produced in an adjoiningcracking vessel, and may originate from any available source of aceticanhydride. Furthermore, it should be noted that the acetylating reagentis not limited to acetic anhydride, as any acetylating reagent can beemployed in the present invention. Once in acetylation vessel 10, theacetic anhydride acts to acetylate the wood according to the followingreaction:

As the foregoing equation illustrates, the acetylation of wood withacetic anhydride produces acetylated wood and acetic acid as abyproduct. In one embodiment, at least a portion of the acetic acidproduced during the acetylation process can be recycled back to holdingtank 12 via line 24, where it can be combined with fresh acetic acidintroduced via line 14. Thus, at least a portion of the acetic acidbyproduct can be continually reused.

However, a portion of the acetic acid originating in the above processcan be removed from acetylation vessel 10. This prevents contaminantsdrawn from the wood from building up in the cycle depicted in FIG. 1.For example, terpenes from the wood can become entrained with the aceticacid resulting from acetylation. Accordingly, at least a portion of theacid-containing composition can be removed from the system asnon-recycled acid-containing composition. The non-recycledacid-containing composition can be withdrawn from acetylation vessel 10via line 26. Alternatively, the non-recycled acid-containing compositioncan be withdrawn from line 24 via line 26 a. It should be noted,however, that the location where the non-recycled acid-containingcomposition is withdrawn is not critical, and can originate from anyportion of the acetylation process. The amount of acid-containingcomposition withdrawn via line 26 and/or line 26 a can be in the rangeof from about 0.01 to about 25 weight percent, in the range of fromabout 0.05 to about 15 weight percent, or in the range of from 0.1 to 5weight percent of the total amount of acid-containing compositionwithdrawn from acetylation vessel 10.

As mentioned above, at least a portion of the acid-containingcomposition originating from esterification of a lignocellulosicmaterial can be employed in a process for making carboxylic acids. Anycarboxylic acid production process that involves oxidizing an oxidizablecompound in the presence of a solvent can be employed in the presentinvention. As used herein, a “carboxylic acid production process” and a“TPA production process” are defined as beginning with an initialoxidation step and ending with a carboxylic acid product, and can, butneed not necessarily, include therein one or more purification steps,concentration steps, isolation steps, purge steps, and/or additionaloxidation steps.

FIG. 2 illustrates a carboxylic acid production process suitable for usein the present invention. In the embodiment illustrated in FIG. 2, apredominately fluid-phase feed stream containing an oxidizable compound(e.g., para-xylene), a solvent (e.g., acetic acid and/or water), and acatalyst system (e.g., cobalt, manganese, and/or bromine) can beintroduced into oxidation zone 110. A predominately gas-phase oxidantstream containing molecular oxygen can also be introduced into oxidationzone 110. The fluid- and gas-phase feed streams form a multi-phasereaction medium in oxidation zone 110. The oxidizable compound canundergo partial oxidation in a liquid phase of the reaction mediumcontained in oxidation zone 110.

In one embodiment of the present invention, oxidation zone 110 cancomprise an agitated reactor. Agitation of the reaction medium inoxidation zone 110 can be provided by any means known in the art. Asused herein, the term “agitation” shall denote work dissipated into thereaction medium causing fluid flow and/or mixing. In one embodiment,oxidation zone 110 can be a mechanically-agitated reactor equipped withmeans for mechanically agitating the reaction medium. As used herein,the term “mechanical agitation” shall denote agitation of the reactionmedium caused by physical movement of a rigid or flexible element(s)against or within the reaction medium. For example, mechanical agitationcan be provided by rotation, oscillation, and/or vibration of internalstirrers, paddles, vibrators, or acoustical diaphragms located in thereaction medium. In another embodiment of the present invention,oxidation zone 110 can comprise a bubble column reactor. As used herein,the term “bubble column reactor” shall denote a reactor for facilitatingchemical reactions in a multi-phase reaction medium, wherein agitationof the reaction medium is provided primarily by the upward movement ofgas bubbles through the reaction medium.

The oxidizable compound present in the fluid-phase feed streamintroduced into oxidation zone 110 can comprise at least one hydrocarbylgroup. Also, the oxidizable compound can comprise an aromatic compound.In one embodiment, the oxidizable compound can comprise an aromaticcompound with at least one attached hydrocarbyl group or at least oneattached substituted hydrocarbyl group or at least one attachedheteroatom or at least one attached carboxylic acid function (—COOH). Inanother embodiment, the oxidizable compound can comprise an aromaticcompound with at least one attached hydrocarbyl group or at least oneattached substituted hydrocarbyl group with each attached groupcomprising from 1 to 5 carbon atoms. In yet another embodiment, theoxidizable compound can be an aromatic compound having exactly twoattached groups with each attached group comprising exactly one carbonatom and consisting of methyl groups and/or substituted methyl groupsand/or at most one carboxylic acid group. Suitable examples of theoxidizable compound include, but are not limited to, para-xylene,meta-xylene, para-tolualdehyde, meta-tolualdehyde, para-toluic acid,meta-toluic acid, and/or acetaldehyde. In one embodiment of the presentinvention, the oxidizable compound comprises para-xylene.

A “hydrocarbyl group,” as defined herein, is at least one carbon atomthat is bonded only to hydrogen atoms and/or to other carbon atoms. A“substituted hydrocarbyl group,” as defined herein, is at least onecarbon atom bonded to at least one heteroatom and to at least onehydrogen atom. “Heteroatoms,” as defined herein, are all atoms otherthan carbon and hydrogen atoms. “Aromatic compounds,” as defined herein,comprise an aromatic ring and can comprise at least 6 carbon atoms andcan also comprise only carbon atoms as part of the ring. Suitableexamples of such aromatic rings include, but are not limited to,benzene, biphenyl, terphenyl, naphthalene, and other carbon-based fusedaromatic rings.

The amount of oxidizable compound present in the fluid-phase feed streamintroduced into oxidation zone 110 can be in the range of from about 4to about 20 weight percent, or in the range of from 6 to 15 weightpercent.

The solvent present in the fluid-phase feed stream introduced intooxidation zone 110 can comprise an acid component and a water component.The solvent can be present in the fluid-phase feed stream at aconcentration in the range of from about 60 to about 98 weight percent,in the range of from about 80 to about 96 weight percent, or in therange of from 85 to 94 weight percent. The acid component of the solventcan be an organic low molecular weight monocarboxylic acid having from 1to 6 carbon atoms, or 2 carbon atoms. In one embodiment, the acidcomponent of the solvent can comprise acetic acid. The acid componentcan make up at least about 75 weight percent of the solvent, at leastabout 80 weight percent of the solvent, or in the range of from 85 to 98weight percent of the solvent, with the balance being primarily water.

In one embodiment of the present invention, at least a portion of thesolvent present in the fluid-phase feed stream introduced into oxidationzone 110 can comprise an acid-containing composition originating fromesterification of a lignocellulosic material, as described above.Furthermore, either additionally or alternatively, an acid-containingcomposition can be introduced into oxidation zone 110 as a separate feedstream (not depicted). As mentioned above, the acid-containingcomposition can comprise acetic acid. In addition, the acid-containingcomposition suitable for use in a carboxylic acid production process cancomprise acetic anhydride and/or one or more terpenes. In oneembodiment, the acid-containing composition can comprise aceticanhydride in an amount of at least about 0.01 weight percent, at leastabout 0.05 weight percent, or at least 0.1 weight percent based on theweight of the acid in the acid-containing composition. Additionally, theacid-containing composition can comprise terpenes in a combined amountof at least about 0.01 weight percent, at least about 0.04 weightpercent, or at least 0.08 weight percent based on the weight of the acidin the acid-containing composition. Furthermore, the one or moreterpenes in the acid-containing composition can comprise limonene.

Though not wishing to be bound by theory, it is believed that thepresence of acetic anhydride in the solvent employed during oxidationwill consume some of the water produced in the oxidation process. Thisis because water readily reacts with acetic anhydride to form aceticacid. As depicted in FIG. 2, ordinarily water is removed from oxidationzone 110 along with the off gas via line 112 in the form of vapor. Offgas in line 112 can have a water content of at least about 4 weightpercent, at least about 8 weight percent, or at least 12 weight percent.

The off gas in line 112 can first be treated in condenser 114 to therebyform a condensed off gas being predominately in liquid phase. Thecondensed off gas can then be routed to water column 118 via line 116.In water column 118, the water can be separated from other solventsremoved with the off gas. Solvent separated from the condensed off gasin water column 118 can be removed via line 122. The solvent in line 122can be substantially comprised of acetic acid. The separated water canbe removed as waste water from water column 118 via line 120. Generally,the waste water in line 120 can have a water content of at least about85 weight percent, at least about 95 weight percent, or at least 99weight percent.

In one embodiment, though not depicted, energy can be recovered from thewaste water in line 120, which can at least partially be in the form ofsteam. In one embodiment, the waste water in line 120 can have atemperature in the range of from about 100 to about 175° C., in therange of from about 115 to about 160° C., or in the range of from 130 to145° C. Additionally, the waste water in line 120 can have a pressure inthe range of from about 60 to about 120 pounds per square inch absolute(psia), or in the range of from 80 to 100 psia.

Any known method in the art suitable for converting at least a portionof the energy of steam into work can be employed for energy recovery inthe present invention. In one embodiment, energy can be recovered fromthe waste water in line 120 by introducing at least a portion of thewaste water into a turboexpander (not depicted), which can convert atleast a portion of the energy of the waste water into work. In anotherembodiment, energy can be recovered by employing at least a portion ofthe waste water in line 120 to heat the working fluid in an organicRankine cycle (not depicted).

The above-described process of removing water and treating the off gasfrom oxidation zone 110 can be time consuming and costly. The process,though, could be done more quickly and with lower cost if less water hadto be withdrawn from oxidation zone 110. As mentioned above, it isbelieved that the residual acetic anhydride in the acid-containingcomposition from the esterification of a lignocellulosic material canaccomplish this task by consuming some of the water produced duringoxidation. Accordingly, the use of an acid-containing composition from alignocellulosic material esterification process has the unexpectedbenefit of lowering production costs associated with a carboxylic acidproduction process. In one embodiment, at least about 10 weight percent,at least about 50 weight percent, or at least 90 weight percent of theacetic anhydride in the solvent reacts with water in oxidation zone 110to produce an acid.

Another unexpected result of employing an acid-containing compositionfrom the esterification of a lignocellulosic material concerns thepresence of terpenes. Ordinarily, the presence of terpenes renders asolvent unsuitable for use in processes that may typically employ anacid-containing solvent (e.g., a solvent containing acetic acid). Thisis because such processes usually cause the terpenes to convert into taror other substances that can foul equipment being employed in theseprocesses. However, in the current invention, the inventors havediscovered that terpenes tend to oxidize in the process employed, thustypically forming carbon dioxide. Furthermore, though not wishing to bebound by theory, it is believed that some terpenes will convert intocarboxylic acids. Accordingly, the presence of terpenes in a carboxylicacid production process is not believed to cause damage to the equipmentemployed. Thus, while an acid-containing composition from theesterification of a lignocellulosic material may not be suitable in manyother processes, it is unexpectedly suited for use as at least a portionof the solvent employed in a carboxylic acid production process.

As mentioned above, the fluid-phase feed stream introduced intooxidation zone 110 can also include a catalyst system. The catalystsystem can be a homogeneous, liquid-phase catalyst system capable ofpromoting at least partial oxidation of the oxidizable compound. Also,the catalyst system can comprise at least one multivalent transitionmetal. In one embodiment, the catalyst system can comprise cobalt,bromine, and/or manganese.

When cobalt is present in the catalyst system, the fluid-phase feedstream can comprise cobalt in an amount such that the concentration ofcobalt in the liquid phase of the reaction medium is maintained in therange of from about 300 to about 6,000 parts per million by weight(ppmw), in the range of from about 700 to about 4,200 ppmw, or in therange of from 1,200 to 3,000 ppmw. When bromine is present in thecatalyst system, the fluid-phase feed stream can comprise bromine in anamount such that the concentration of bromine in the liquid phase of thereaction medium is maintained in the range of from about 300 to about5,000 ppmw, in the range of from about 600 to about 4,000 ppmw, or inthe range of from 900 to 3,000 ppmw. When manganese is present in thecatalyst system, the fluid-phase feed stream can comprise manganese inan amount such that the concentration of manganese in the liquid phaseof the reaction medium is maintained in the range of from about 20 toabout 1,000 ppmw, in the range of from about 40 to about 500 ppmw, or inthe range of from 50 to 200 ppmw.

In one embodiment of the present invention, cobalt and bromine can bothbe present in the catalyst system. The weight ratio of cobalt to bromine(Co:Br) in the catalyst system can be in the range of from about 0.25:1to about 4:1, in the range of from about 0.5:1 to about 3:1, or in therange of from 0.75:1 to 2:1. In another embodiment, cobalt and manganesecan both be present in the catalyst system. The weight ratio of cobaltto manganese (Co:Mn) in the catalyst system can be in the range of fromabout 0.3:1 to about 40:1, in the range of from about 5:1 to about 30:1,or in the range of from 10:1 to 25:1.

During oxidation, the ratio of the mass flow rate of the solvent to themass flow rate of the oxidizable compound (e.g., para-xylene) enteringoxidation zone 110 can be maintained in the range of from about 2:1 toabout 50:1, in the range of from about 5:1 to about 40:1, or in therange of from 7.5:1 to 25:1.

The predominately gas-phase oxidant stream introduced into oxidationzone 110 can comprise in the range of from about 5 to about 40 molepercent molecular oxygen, in the range of from about 15 to about 30 molepercent molecular oxygen, or in the range of from 18 to 24 mole percentmolecular oxygen. The balance of the oxidant stream can be comprisedprimarily of a gas or gases, such as nitrogen, that are inert tooxidation. In one embodiment, the oxidant stream consists essentially ofmolecular oxygen and nitrogen. In another embodiment, the oxidant streamcan be dry air that comprises about 21 mole percent molecular oxygen andabout 78 to about 81 mole percent nitrogen. In an alternative embodimentof the present invention, the oxidant stream can comprise substantiallypure oxygen.

During liquid-phase oxidation in oxidation zone 110, the oxidant streamcan be introduced into oxidation zone 110 in an amount that providesmolecular oxygen somewhat exceeding the stoichiometric oxygen demand.Thus, the ratio of the mass flow rate of the oxidant stream (e.g., air)to the mass flow rate of the oxidizable compound (e.g., para-xylene)entering oxidation zone 110 can be maintained in the range of from about0.5:1 to about 20:1, in the range of from about 1:1 to about 10:1, or inthe range of from 2:1 to 6:1.

The liquid-phase oxidation reaction carried out in oxidation zone 110can be a precipitating reaction that generates solids. In oneembodiment, the liquid-phase oxidation carried out in oxidation zone 110can cause at least about 10 weight percent of the oxidizable compound(e.g., para-xylene) introduced into oxidation zone 110 to form solids(e.g., crude terephthalic acid (“CTA”) particles) in the reactionmedium. In another embodiment, the liquid-phase oxidation carried out inoxidation zone 110 can cause at least about 50 weight percent of theoxidizable compound (e.g., para-xylene) introduced into oxidation zone110 to form solids (e.g., CTA particles) in the reaction medium. In yetanother embodiment, the liquid-phase oxidation carried out in oxidationzone 110 can cause at least about 90 weight percent of the oxidizablecompound (e.g., para-xylene) introduced into oxidation zone 110 to formsolids (e.g., CTA particles) in the reaction medium. In one embodiment,the solids content of the reaction medium can be maintained in the rangeof from about 1 to about 50 weight percent, in the range of from about 5to about 40 weight percent, in the range of from about 10 to about 35weight percent, or in the range of from 15 to 30 weight percent. As usedherein, the term “solids content” shall denote the weight percent solidsin a multi-phase mixture.

During oxidation in oxidation zone 110, the multi-phase reaction mediumcan be maintained at an elevated temperature in the range of from about125 to about 200° C., in the range of from about 150 to about 180° C.,or in the range of from 155 to 165° C. The overhead pressure inoxidation zone 110 can be maintained in the range of from about 1 toabout 20 bar gauge (barg), in the range of from about 2 to about 12barg, or in the range of from 4 to 8 barg.

In the embodiment of FIG. 2, a crude slurry can be withdrawn from anoutlet of oxidation zone 110 via line 124. The solid phase of the crudeslurry in line 124 can be formed primarily of CTA particles. The liquidphase of the crude slurry in line 124 can be a liquid mother liquorcomprising at least a portion of the solvent, one or more catalystcomponents, and minor amounts of dissolved terephthalic acid (“TPA”). Inone embodiment, the crude slurry in line 124 can comprise acetic acid inan amount of at least about 10 weight percent. The solids content of thecrude slurry in line 124 can be the same as the solids content of thereaction medium in oxidation zone 110, discussed above. In anotherembodiment, the crude slurry in line 124 can have a solids content of atleast about 15 weight percent.

In one embodiment of the present invention, the crude slurry in line 124can comprise impurities. As used herein, the term “impurities” isdefined as any substance other than TPA, solvent, catalyst, and water.Such impurities can include oxidation byproducts formed during the atleast partial oxidation of the above-mentioned oxidizable compound(e.g., para-xylene) including, but not limited to, benzoic acid (BA),bromo-benzoic acid, bromo-acetic acid, isophthalic acid, trimelliticacid, 2,5,4′-tricarboxybiphenyl, 2,5,4′-tricarboxybenzophenone,para-toluic acid (p-TAc), 4-carboxybenzaldehyde (4-CBA),monocarboxyfluorenones, monocarboxyfluorenes, dicarboxyfluorenes, and/ordicarboxyfluorenones.

Subsequent to removal from oxidation zone 110, at least a portion of thecrude slurry can be introduced into purification zone 126 via line 124.In one embodiment, the crude slurry can be treated in purification zone126 such that the concentration of at least one of the above-mentionedimpurities in the crude slurry is reduced, thereby producing a purifiedslurry. Such reduction in the concentration of impurities in the TPA canbe accomplished by oxidative digestion, hydrogenation, and/ordissolution/recrystallization.

In one embodiment of the present invention, the crude slurry fed topurification zone 126 can have a 4-CBA content of at least about 100parts per million based on the weight of the solids in the crude slurry(ppmwcs), in the range of from about 200 to about 10,000 ppmwcs, or inthe range of from 800 to 5,000 ppmwcs. The crude slurry fed topurification zone 126 can have a p-TAc content of at least about 250ppmwcs, in the range of from about 300 to about 5,000 ppmwcs, or in therange of from 400 to 1,500 ppmwcs. The purified slurry exitingpurification zone 126 can have a 4-CBA content of less than about 150parts per million based on the weight of the solids in the purifiedslurry (ppmwps), less than about 100 ppmwps, or less than 50 ppmwps. Thepurified slurry exiting purification zone 126 can have a p-TAc contentof less than about 300 ppmwps, less than about 200 ppmwps, or less than150 ppmwps. In one embodiment, treatment of the crude slurry inpurification zone 126 can cause the purified slurry exiting purificationzone 126 to have a 4-CBA and/or p-TAc content that is at least about 50percent less than the 4-CBA and/or p-TAc content of the crude slurry fedto purification zone 126, at least about 85 percent less, or at least 95percent less. By way of illustration, if the 4-CBA content of the crudeslurry fed to purification zone 126 is 200 ppmwcs and the 4-CBA contentof the purified slurry exiting purification zone 126 is 100 ppmwps, thenthe 4-CBA content of the purified slurry is 50 percent less than the4-CBA content of the crude slurry.

In one embodiment of the present invention, the crude slurry can besubjected to purification by oxidative digestion in purification zone126. As used herein, the term “oxidative digestion” denotes a processstep or steps where a feed comprising solid particles is subjected tooxidation under conditions sufficient to permit oxidation of at least aportion of the impurities originally trapped in the solid particles.Purification zone 126 can comprise one or more reactors or zones. In oneembodiment, purification zone 126 can comprise one or moremechanically-agitated reactors. A secondary oxidant stream, which canhave the same composition as the gas-phase oxidant stream fed tooxidation zone 110, can be introduced into purification zone 126 toprovide the molecular oxygen required for oxidative digestion.Additional oxidation catalyst can be added if necessary. In analternative embodiment of the present invention, a stream comprisinghydrogen can be introduced into purification zone 126 for at leastpartial hydrogenation of the crude slurry.

When oxidative digestion is employed in purification zone 126, thetemperature at which oxidative digestion is carried out can be at leastabout 10° C. greater than the temperature of oxidation in oxidation zone110, in the range of from about 20 to about 80° C. greater, or in therange of from 30 to 50° C. greater. The additional heat required for theoperation of purification zone 126 can be provided by supplying avaporized solvent to purification zone 126 and allowing the vaporizedsolvent to condense therein. The oxidative digestion temperature inpurification zone 126 can be maintained in the range of from about 180to about 240° C., in the range of from about 190 to about 220° C., or inthe range of from 200 to 210° C. The oxidative digestion pressure inpurification zone 126 can be maintained in the range of from about 100to about 350 pounds per square inch gauge (psig), in the range of fromabout 175 to about 275 psig, or in the range of from 185 to 225 psig.

In one embodiment of the present invention, purification zone 126 caninclude two digestion reactors/zones—an initial digester and a finaldigester. When purification zone 126 includes an initial digester and afinal digester, the final digester can be operated at a lowertemperature and pressure than the initial digester. In one embodiment,the operating temperature of the final digester can be at least about 2°C. lower than the operating temperature of the initial digester, or inthe range of from about 5 to about 15° C. lower than the operatingtemperature of the initial digester. In one embodiment, the operatingpressure of the final digester can be at least about 5 psig lower thanthe operating pressure of the initial digester, or in the range of fromabout 10 to about 50 psig lower than the operating pressure of theinitial digester. The operating temperature of the initial digester canbe in the range of from about 195 to about 225° C., in the range of from205 to 215° C., or about 210° C. The operating pressure of the initialdigester can be in the range of from about 215 to about 235 psig, orabout 225 psig. The operating temperature of the final digester can bein the range of from about 190 to about 220° C., in the range of from200 to 210° C., or about 205° C. The operating pressure of the finaldigester can be in the range of from about 190 to 210 psig, or about 200psig.

In one embodiment of the present invention, purification zone 126 cancomprise optional first and second solvent swap zones. Optional firstand second solvent swap zones can operate to replace at least a portionof the existing solvent in a slurry with a replacement solvent.Equipment suitable for such replacement includes, but is not limited to,a decanter centrifuge followed by a reslurry with replacement solvent, adisc stack centrifuge, an advancing front crystallizer, or multipledecanter centrifuges with optional counter current washing. Thereplacement oxidation solvent can have substantially the samecomposition as the solvent introduced into oxidation zone 110, asdescribed above. Additionally, the replacement oxidation solvent cancomprise at least a portion of the acid-containing compositionoriginating from the above-described esterification of lignocellulosicmaterial.

In one embodiment, the crude slurry fed to purification zone 126 can betreated in the optional first solvent swap zone prior to purification ofthe crude slurry by the above-mentioned oxidative digestion. In anotherembodiment, a purified slurry resulting from oxidative digestion of thecrude slurry can be treated in the optional second solvent swap zone. Inone embodiment, at least a portion of the displaced oxidation solventfrom the optional first and/or second solvent swap zones can bedischarged from purification zone 126 via line 128. At least a portionof the displaced oxidation solvent in line 128 can be routed to purgetreatment zone 162 via line 130, and/or oxidation zone 110 via line 132.

In another embodiment of the present invention, purification zone 126can comprise an optional crystallization zone and/or an optional coolingzone. A purified slurry resulting from the above-mentioned oxidativedigestion of the crude slurry can be treated in the optionalcrystallization zone to at least partially increase the particle sizedistribution of the purified slurry. Optional crystallization zone cancomprise any equipment known in the art that can operate to increase theparticle size distribution of the purified slurry. When an optionalcooling zone is employed, the purified slurry can be cooled therein to atemperature in the range of from about 20 to about 195° C. When both acrystallization zone and a cooling zone are employed, the purifiedslurry can be treated first in the crystallization zone and subsequentlyin the cooling zone.

Referring still to FIG. 2, a purified slurry can be withdrawn from anoutlet of purification zone 126 via line 134. The solid phase of thepurified slurry can be formed primarily of purified terephthalic acid(PTA) particles, while the liquid phase can be formed of a motherliquor. The solids content of the purified slurry in line 134 can be inthe range of from about 1 to about 50 percent by weight, in the range offrom about 5 to about 40 weight percent, or in the range of from 20 to35 weight percent. In one embodiment of the present invention, at leasta portion of the purified slurry in line 134 can be employed as anisolation feed slurry which can be introduced into product isolationzone 136.

Product isolation zone 136 can separate the crude slurry and/or thepurified slurry into a predominately fluid phase mother liquor and a TPAproduct wet cake. Product isolation zone 136 can comprise any method ofsolid/liquid separation known in the art that is capable of generating awet cake and a mother liquor stream. In addition, it may be desirablefor product isolation zone 136 to have the capability of washing the wetcake. Suitable equipment for use in product isolation zone 136 includes,but is not limited to, a pressure drum filter, a vacuum drum filter, avacuum belt filter, multiple solid bowl centrifuges with optionalcounter current wash, or a perforated centrifuge.

In one embodiment of the present invention, a wash stream can beintroduced into product isolation zone 136 to wash at least a portion ofthe wet cake generated in product isolation zone 136, thereby producinga washed wet cake. In one embodiment, the wash stream can compriseacetic acid and/or water. Optionally, after washing the wet cake, theused wash liquor can be withdrawn from product isolation zone 136, andat least a portion of the wash liquor can be routed, either directly orindirectly, to oxidation zone 110.

The above-mentioned wet cake generated in product isolation 136 canprimarily comprise solid particles of TPA. The solid TPA particles cancomprise CTA and/or PTA particles. The wet cake can comprise in therange of from about 5 to about 30 weight percent liquid, in the range offrom about 10 to about 25 weight percent liquid, or in the range of from12 to 23 weight percent liquid. Additionally, the TPA product wet cakecan comprise oxidation byproducts, as discussed above. In oneembodiment, the TPA product can comprise a cumulative concentration ofmono-functional oxidation byproducts of less than about 1,000 ppmw, lessthan about 750 ppmw, or less than 500 ppmw.

In one embodiment of the present invention, the wet cake produced inproduct isolation zone 136 can be introduced into a drying zone (notshown) to thereby produce a dry TPA particulate product comprising solidTPA particles. The drying zone can comprise any drying device known inthe art that can produce a dried TPA particulate product comprising lessthan about 5 weight percent liquid, less than about 3 weight percentliquid, or less than 1 weight percent liquid.

In another embodiment, the wet cake produced in product isolation zone136 can be introduced into a solvent swap zone (not shown) to produce awet TPA particulate product comprising solid TPA particles. The solventswap zone can operate to replace at least a portion of the liquid in thewet cake with a replacement solvent. Equipment suitable for suchreplacement includes, but is not limited to, a decanter centrifugefollowed by a reslurry with replacement solvent, a disc stackcentrifuge, an advancing front crystallizer, or multiple decantercentrifuges with counter current washing. The wet TPA particulateproduct can comprise in the range of from about 5 to about 30 weightpercent liquid, in the range of from about 10 to about 25 weight percentliquid, or in the range of from 12 to 23 weight percent liquid.

Referring still to FIG. 2, the above-mentioned mother liquor can bedischarged from product isolation zone 136 via line 138. In oneembodiment of the present invention, at least a portion of the motherliquor in line 138 can optionally be introduced into a solids removalzone (not shown). A solids removal zone can comprise any equipment knownin the art that is operable to remove a sufficient amount of solids fromthe mother liquor to produce a solids-depleted mother liquor comprisingless than about 5 weight percent solids, less than about 2 weightpercent solids, or less than 1 weight percent solids. Suitable equipmentthat may be employed in a solids removal zone includes a pressurefilter, such as, for example, a filter press, a candle filter, apressure leaf filter, and/or a cartridge filter.

In one embodiment of the present invention, at least a portion of theoptionally solids-depleted mother liquor in line 138 can be withdrawnfrom line 138 via line 140 to form a purge feed stream. The amount ofmother liquor withdrawn by line 140 to form the purge feed stream can bein the range of from about 1 to about 55 percent of the total weight ofthe mother liquor, in the range of from about 5 to about 45 percent byweight, or in the range of from 10 to 35 percent by weight. Optionally,at least a portion of the displaced oxidation solvent discharged frompurification zone 126 in line 130 can be combined with the purge feedstream and introduced into purge treatment zone 162 substantiallysimultaneously. In another embodiment, at least a portion of theremaining mother liquor in line 138 can be routed, either directly orindirectly, to oxidation zone 110 via line 142. Optionally, at least aportion of the wash liquor in line 144 discharged from product isolationzone 136 can be combined with at least a portion of the mother liquor inline 142 prior to introduction into oxidation zone 110.

In one embodiment of the present invention, the mother liquor in line138, and consequently the purge feed stream in line 140, can comprisesolvent, one or more catalyst components, oxidation byproducts, and TPA.The solvent in the mother liquor in line 138 and the purge feed streamin line 140 can comprise a monocarboxylic acid. In one embodiment, thesolvent can comprise water and/or acetic acid. The mother liquor in line138 and the purge feed stream in line 140 can comprise solvent in anamount of at least about 85 weight percent, at least about 95 weightpercent, or at least 99 weight percent.

The catalyst components in the mother liquor in line 138 and the purgefeed stream in line 140 can comprise the catalyst components asdescribed above with reference to the catalyst system introduced intooxidation zone 110 (e.g., cobalt, manganese, and/or bromine). The motherliquor in line 138 and the purge feed stream in line 140 can have acumulative concentration of all of the catalyst components in the rangeof from about 500 to about 20,000 ppmw, in the range of from about 1,000to about 15,000 ppmw, or in the range of from 1,500 to 10,000 ppmw.

The oxidation byproducts in the mother liquor in line 138 and the purgefeed stream in line 140 can comprise one or more of the oxidationbyproducts discussed above. In one embodiment, the oxidation byproductsin the mother liquor in line 138 and the purge feed stream in line 140can comprise both BA and non-BA byproducts. As used herein, the term“non-BA byproducts” is defined as any oxidation byproduct that is notbenzoic acid. Non-BA byproducts include, but are not limited to,isophthalic acid (IPA), phthalic acid (PA), trimellitic acid,2,5,4′-tricarboxybiphenyl, 2,5,4′-tricarboxybenzophenone, p-TAc, 4-CBA,naphthalene dicarboxylic acid, monocarboxyfluorenones,monocarboxyfluorenes, dicarboxyfluorenes, and/or dicarboxyfluorenones.In one embodiment, the mother liquor in line 138 and the purge feedstream in line 140 can comprise BA in an amount in the range of fromabout 500 to about 150,000 ppmw based on the weight of the purge feedstream, in the range of from about 1,000 to about 100,000 ppmw, or inthe range of from 2,000 to 50,000 ppmw. Additionally, the mother liquorin line 138 and the purge feed stream in line 140 can have a cumulativeconcentration of non-BA byproducts in the range of from about 500 toabout 50,000 ppmw, in the range of from about 1,000 to about 20,000ppmw, or in the range of from 2,000 to 10,000 ppmw.

In one embodiment of the present invention, the mother liquor in line138 and the purge feed stream in line 140 can comprise solids in anamount of less than about 5 weight percent, less than about 2 weightpercent, or less than 1 weight percent. Additionally, the purge feedstream can have a temperature of less than about 240° C., in the rangeof from about 20 to about 200° C., or in the range of from 50 to 100° C.

Referring still to FIG. 2, the purge feed stream can be introduced intopurge treatment zone 162 via line 140. Purge treatment zone 162 canseparate the purge feed stream into a catalyst rich stream and a purgestream. The catalyst rich stream can be discharged from purge treatmentzone 162 via line 150, and the purge stream can be discharged via line146.

The catalyst rich stream in line 150 can have a relatively highercumulative concentration of all of the catalyst components on a weightbasis compared to the cumulative concentration of all of the catalystcomponents in the purge feed stream in line 140. In one embodiment ofthe present invention, the catalyst rich stream in line 150 can have acumulative concentration of all of the catalyst components that is atleast about 1.5 times the cumulative concentration of all of thecatalyst components in the purge feed stream on a weight basis, at leastabout 5 times the cumulative concentration of all of the catalystcomponents in the purge feed stream on a weight basis, or at least 10times the cumulative concentration of all of the catalyst components inthe purge feed stream on a weight basis. Depending of the temperatureand pressure of the catalyst rich stream upon exiting purge treatmentzone 162, the catalyst rich stream in line 150 can predominatelycomprise solids or fluid. Thus, in one embodiment, the catalyst richstream in line 150 can comprise at least about 50 weight percent fluid,at least about 70 weight percent fluid, or at least 90 weight percentfluid. In an alternate embodiment, the catalyst rich stream in line 150can comprise at least about 50 weight percent solids, at least about 70weight percent solids, or at least 90 weight percent solids.

In one embodiment of the present invention, at least a portion of thecatalyst rich stream in line 150 can be routed, either directly orindirectly, to oxidation zone 110, where at least about 50 weightpercent, at least about 60 weight percent, or at least 70 weight percentof the catalyst components of the catalyst rich stream are introducedinto oxidization zone 110. In one embodiment, prior to routing, a liquidcan optionally be added to the catalyst rich stream in line 150 toproduce a reslurried catalyst rich stream. The optional reslurriedcatalyst rich stream can comprise at least about 35 weight percentliquid, at least about 50 weight percent liquid, or at least 65 weightpercent liquid. The liquid added to the catalyst rich stream can be, forexample, acetic acid and/or water.

It will be understood by one skilled in the art that each of theabove-described embodiments, as well as any sub-parts of thoseembodiments, may be operated in a continuous or a non-continuous manner.Non-continuous operations include, but are not limited to, batch-wiseoperations, cyclical operations, and/or intermittent operations. In someof the embodiments above, temperature ranges are provided for aspecified operation. For each of the above embodiments where atemperature range is provided, the temperature is defined as the averagetemperature of the substance in the given zone or section.

Numerical Ranges

The present description uses numerical ranges to quantify certainparameters relating to the invention. It should be understood that whennumerical ranges are provided, such ranges are to be construed asproviding literal support for claim limitations that only recite thelower value of the range as well as claims limitation that only recitethe upper value of the range. For example, a disclosed numerical rangeof 10 to 100 provides literal support for a claim reciting “greater than10” (with no upper bounds) and a claim reciting “less than 100” (with nolower bounds).

Definitions

As used herein, the terms “a,” “an,” “the,” and “said” mean one or more.

As used herein, the term “and/or,” when used in a list of two or moreitems, means that any one of the listed items can be employed by itselfor any combination of two or more of the listed items can be employed.For example, if a composition is described as containing components A,B, and/or C, the composition can contain A alone; B alone; C alone; Aand B in combination; A and C in combination; B and C in combination; orA, B, and C in combination.

As used herein, the terms “comprising,” “comprises,” and “comprise” areopen-ended transition terms used to transition from a subject recitedbefore the term to one or more elements recited after the term, wherethe element or elements listed after the transition term are notnecessarily the only elements that make up the subject.

As used herein, the terms “containing,” “contains,” and “contain” havethe same open-ended meaning as “comprising,” “comprises,” and “comprise”provided above.

As used herein, the terms “having,” “has,” and “have” have the sameopen-ended meaning as “comprising,” “comprises,” and “comprise” providedabove.

As used herein, the terms “including,” “includes,” and “include” havethe same open-ended meaning as “comprising,” “comprises,” and “comprise”provided above.

Claims not Limited to the Disclosed Embodiments

The preferred forms of the invention described above are to be used asillustration only, and should not be used in a limiting sense tointerpret the scope of the present invention. Modifications to theexemplary embodiments, set forth above, could be readily made by thoseskilled in the art without departing from the spirit of the presentinvention.

The inventors hereby state their intent to rely on the Doctrine ofEquivalents to determine and assess the reasonably fair scope of thepresent invention as pertains to any apparatus not materially departingfrom but outside the literal scope of the invention as set forth in thefollowing claims.

What is claimed is:
 1. A process for producing an aromatic carboxylicacid, said process comprising oxidizing an oxidation feed comprising atleast one oxidizable compound and at least one solvent comprising amonocarboxylic acid, wherein at least a portion of said monocarboxylicacid originated from a wood acetylation process, wherein said solventfurther comprises one or more terpenes, wherein said oxidizable compoundcomprises para-xylene, wherein said carboxylic acid comprisesterephthalic acid.
 2. The process of claim 1, wherein said solventfurther comprises acetic anhydride in an amount of at least 0.01 weightpercent based on the weight of monocarboxylic acid employed from saidwood acetylation process.
 3. The process of claim 2, wherein saidoxidizing produces water as a byproduct, wherein at least a portion ofsaid acetic anhydride consumes at least a portion of said water.
 4. Theprocess of claim 1, wherein said monocarboxylic acid comprises aceticacid, wherein at least 5 weight percent of said acetic acid is aceticacid originated from said wood acetylation process.
 5. The process ofclaim 1, wherein said solvent comprises a combined concentration of allof said terpenes in an amount of at least 0.01weight percent based onthe weight of acetic acid employed from said wood acetylation process.6. The process of claim 1, said process further comprising at least onepurification step.
 7. A process for producing an aromatic carboxylicacid, said process comprising: (a) contacting at least onelignocellulosic material with a compound containing at least one acetylgroup to thereby produce an acetylated lignocellulosic material and anacid-containing composition; and (b) introducing at least a portion ofsaid acid-containing composition and an oxidizable compound into acarboxylic acid production process, wherein said acid-containingcomposition comprises acetic acid; wherein said acid-containingcomposition further comprises one or more terpenes in an amount of atleast 0.01 weight percent based on the weight of said acetic acid insaid acid-containing compositions.
 8. The process of claim 7, whereinsaid acid-containing composition further comprises acetic anhydride inan amount of at least 0.01 weight percent based on the weight of saidacetic acid in said acid-containing composition.
 9. The process of claim8, wherein said carboxylic acid production process comprises anoxidation reactor, wherein said process further comprises oxidizing atleast a portion of said oxidizable compound in the presence of at leasta portion of said acid-containing composition in said oxidation reactor,wherein said oxidizing produces water as a byproduct, wherein at least aportion of said acetic anhydride consumes at least a portion of saidwater.
 10. The process of claim 7, wherein said lignocellulosic materialcomprises wood, wherein said compound containing at least one acetylgroup comprises acetic anhydride in an amount of at least 50 weightpercent.
 11. The process of claim 7, wherein said oxidizable compoundcomprises para-xylene, wherein said carboxylic acid comprisesterephthalic acid.
 12. The process of claim 7, wherein said carboxylicacid production process further comprises at least one purificationstep.
 13. A process for producing an aromatic carboxylic acid, saidprocess comprising oxidizing an oxidizable compound in an oxidationreactor in the presence of at least one solvent comprises acetic acid,wherein said solvent further comprises acetic anhydride in an amount ofat least 0.01 weight percent based on the total weight of the solvent;wherein said solvent comprises terpenes in a cumulative amount of atleast 0.01 weight percent based on the total weight of the solvent. 14.The process of claim 13, wherein said solvent comprises acetic anhydridein an amount of at least 0.05 weight percent based on the total weightof the solvent.
 15. The process of claim 13, wherein at least a portionof said terpenes are oxidized in said oxidation reactor to form carbondioxide,
 16. The process of claim 13, wherein said oxidizing produceswater as a byproduct, wherein at least a portion of said aceticanhydride consumes at least a portion of said water.
 17. The process ofclaim 13, wherein at least a portion of said solvent originates from awood acetylation process.
 18. The process of claim 13, wherein saidsolvent further comprises acetic acid and/or water, wherein saidcarboxylic acid comprises terephthalic acid, wherein said oxidizablecompound comprises para-xylene.
 19. The process of claim 13, saidprocess further comprising at least one purification step.